Electrophotography – Having particular structure – Modular or displaceable
Reexamination Certificate
2002-09-23
2004-12-28
Beatty, Robert (Department: 2852)
Electrophotography
Having particular structure
Modular or displaceable
C399S228000, C399S299000
Reexamination Certificate
active
06836630
ABSTRACT:
FIELD OF THE INVENTION
The invention claimed and disclosed herein pertains to multi-color imaging apparatus, and more particularly to methods and apparatus for reducing wear on selected toner distribution components within a multi-color imaging apparatus.
BACKGROUND OF THE INVENTION
Multi-color imaging apparatus are well known in the art. Such imaging apparatus can include printers, photocopiers, and multi-function imaging apparatus. Multi-function imaging apparatus typically include the capability to function as a printer and a photocopier, and can include other capability as well, such as performing the functions of a facsimile machine. By “multi-color” we mean that the imaging apparatus can produce an image having two or more colors, which can include black as a color. Typically, multi-color imaging apparatus are four-color imaging apparatus, which use four base imaging substances (ink or toner) of yellow, magenta, cyan and black to allow a palette of a large number of colors to be imaged. This is typically accomplished by imposing the base colors on top of one another, or in close proximity to one another, and can be enhanced by varying the density of the applied base colors relative to one another. Multi-color imaging apparatus can take the form of liquid ink-jet printing devices, as well as electrophotographic imaging apparatus. The present invention is particularly directed to the latter type of color imaging apparatus.
The electrophotographic (“EP”) imaging process is well understood in the art, and need not be described further herein. However, to provide a basis for the following discussion, we will now provide a very brief overview of the EP imaging process. For EP imaging, a light-sensitive optical photoconductor (“OPC”) is provided, which is initially provide with a base charge (either positive or negative). The OPC is then selectively exposed by an exposing device (commonly a scanned laser, but light emitting diodes (“LEDs”) can also be used) to produce at least a portion of an image on the OPC. The selectively exposed OPC is then placed in contact with an imaging substance (here, toner) having a static electrical potential. The toner is then attracted to (or repelled from) the selectively exposed portions of the OPC, such that a portion of the image to be reproduced is placed on the OPC by the toner. The toner on the OPC is then transferred (directly or indirectly) from the OPC to a sheet of imaging media. The imaging media can be a sheet of paper, a transparency, card stock, or other such media. The transfer of the toner from the OPC to the imaging media is typically accomplished using a corona discharge unit or a charged roller which attracts toner away from the OPC and onto the imaging media. The toner on the imaging media is then fixed to the imaging media using a fusing station, which can use heat and/or pressure to fuse the transferred toner to the imaging media.
The imaging substance (toner) used in the EP imaging process is typically provided in a replaceable cartridge (a “toner cartridge”), which can be replaced when the cartridge is depleted of toner or is otherwise deemed to be beyond the useful life of the cartridge (as will be discussed further below). For typical four-color EP imaging, four toner cartridges are provided: a cartridge containing black toner, a cartridge containing yellow toner, a cartridge containing cyan toner, and a cartridge containing magenta toner. Black toner is typically comprised of carbon particles which can be statically electrically charged, and thus black toner is commonly known as a “magnetic” toner. The electro-static properties of black toner allow it to be easily transferred from place-to-place by electrostatic processes. However, toners for the colors yellow, cyan and magenta are typically comprised of plastic or polymeric particles which do not have the electrostatic properties that black toner has. Accordingly, these non-black toners are typically mixed with a transfer agent that has electrostatic properties and attaches to the polymeric color particles, thus facilitating electrostatic transfer of these polymeric particles in the EP imaging process.
For multi-color EP imaging, a number of different configurations are known. They include at least the following:
I) An imaging apparatus configured to receive two or more (typically four) toner cartridges and two or more (typically four) separate OPC cartridges. (See for example U.S. Pat. No. 5,615,002, which is hereby incorporated herein by reference in its entirety). In this configuration, each OPC cartridge is associated with a respective toner cartridge. The OPC cartridges transfer toner from the respective toner cartridges to an intermediate transfer device (either a belt or a drum). The various colors from the toner cartridges are built-up on the intermediate transfer device (“ITD”) to form an image, and the accumulated toner on the ITD is then transferred to a sheet of imaging media to form the final image. This process is commonly known as a “four-pass” imaging process, since the ITD must pass the four OPCs four times to allow all four colors to be accumulated on the ITD. This process allows a wide range of imaging colors since the four colors can be applied on top of one another in various combinations to create a wide range of colors.
II) An imaging apparatus as described immediately above, but wherein the OPCs are incorporated into the toner cartridges. That is, rather than having separate OPC cartridges, the OPCs are part of the respective toner cartridges.
III) An imaging apparatus configured to receive two or more (typically four) toner cartridges, and having a single resident OPC. This configuration provides a low cost multi-color imaging solution. In this configuration, the single resident OPC can be a drum or a belt which can be singly or multiply exposed to form an image thereon. However, due to the difficulty of exposing an OPC through previously developed areas of the OPC (i.e., areas where toner has already been applied to the OPC), in this application the OPC is typically charged only a single time, and then is selectively discharged and selectively exposed to for the four colors. That is, this arrangement typically does not allow for color-on-color toner application to the OPC, but provides for color-next-to-color toner application to the OPC. This arrangement can be described as “single-pass” (versus “four-pass”) color imaging, and allows for a much faster imaging time, but at the cost of a limited palette of colors, and reduced quality of the resulting image.
IV) An imaging apparatus having a rotating carousel configured to receive a plurality (typically four) toner cartridges (each cartridge having a dedicated OPC), and an intermediate transfer device (ITD). The toners of various colors are built-up on the ITD device individually. A first toner cartridge is placed in proximity to the ITD, and after the first toner has been applied to the ITD, the carousel rotates to allow the second toner cartridge to place toner on the ITD. Once all of the toner cartridges have been allowed to place toner on the ITD, and thus build-up the image on the ITD, the resultant image is then transferred from the ITD to a sheet of imaging media.
In each of these configurations there are a number of rotating cylindrical toner transfer devices. These toner transfer devices can include at least the following devices: the OPC; a toner transfer roller to transfer toner from a toner reservoir to the OPC; a charge roller which is used to charge the OPC with a base charge; and a cleaning brush. In some configurations a corona discharge unit is used instead of a charge roller OPC to charge the OPC. Further, the OPC typically is in contact with a cleaning blade which scrapes any residual toner from the OPC before the OPC is recharged. In some applications a doctor blade is in contact with the toner transfer roller to more evenly distribute toner across the transfer roller before the toner is transferred to the OPC. Each time one of these rotating toner transfer devices is cycle
Kumar Jeetendra
Moats Travis
Owen Kevin
Wachter Roman
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